Molded-case electric circuit breaker with contact arm latch

ABSTRACT

The circuit breaker has three ganged movable contact arm structures movable as a unit between open and closed positions by a spring-powered toggle mechanism coupled to a center one of the contact arm structures. The toggle mechanism includes a releasable cradle member which is released upon overload or a fault to permit the toggle mechanism to drive the contact arm structures to open position. A manual operating mechanism is provided for resetting the toggle mechanism when the contact arm structures are in the contact open position and for releasing the reset toggle mechanism for effecting closure of the contacts. During the closing operation, the cradle member interlocks with a latch on the center contact arm structure until the manual operating mechanism defeats the interlock by bending the latch by a camming action.

- United States Patent [72] Inventor Ronald G. Peck Cedar Rapids, Iowa [2]] Appl No. 776,412 [22] Filed Nov. 18, 1968 [45] Patented Feb. 9,1971 [73] Assignee Square D Company Park Ridge, Ill. a corporation of Michigan [54] MOLDED-CASE ELECTRIC CIRCUIT BREAKER WITH CONTACT ARM LATCH 6 Claims, 6 Drawing Figs.

[52] US. Cl 200/169; 335/8 [51] Int. Cl H0lh 3/20, I-lOlh 9/20 {50] Field of Search 200/ 169; 335/8, 164 to 171 [56] References Cited UNITED STATES PATENTS 3,134,879 5/1964 Gauthier et al. 200/169 3,299,244 1/1967 Strobeletal 3,355,685 11/1967 Leonard ABSTRACT: The circuit breaker has three ganged movable contact arm structures movable as a unit between open and closed positions by a spring-powered toggle mechanism coupled to a center one of the contact arm structures. The toggle mechanism includes a releasable cradle member which is released upon overload or a fault to permit the toggle mechanism to drive the contact arm structures to open position. A manual operating mechanism is provided for resetting the toggle mechanism when the contact arm structures are in the contact open position and for releasing the reset toggle mechanism for effecting closure of the contacts. During the closing operation, the cradle member interlocks with a latch on the center contact arm structure until the manual operating mechanism defeats the interlock by bending the latch by a camming action.

PATENTED F EB 9 l9?! SHEET 1 OF 2 INVENTOR. RONALD 6. PECK PATENTEDFEB SIS?! 3,562,469

SHEET 2 [IF 2 INVENTO/P. RONALD G. PECK erg/ @144 MOLDED-CASE ELECTRIC CIRCUIT BREAKER WITH CONTACT ARM LATCH This invention relates to improvements in molded case electric circuit breakers, and more particularly to an improved releasable interlock means or latching mechanism between a contact arm structure and a spring-biased toggle mechanism of the circuit breaker.

Prior molded case circuit breakers, such as disclosed in U. S. Pat. No. 3,355,685, issued Nov. 28, 1967, comprise a contact arm structure pivotable between a contact open position and a contact closed position and a spring-biased toggle mechanism for moving the contact arm structure with a snap action during both the opening and closing movement.

Recently, there has been a demand to provide molded case circuit breakers having much larger current-carrying capacities and interrupting ratings than have heretofore been possible. One of the problems encountered in the design of such circuit breakers is that movement of the manual operating mechanism from an OFF position toward an ON position causes a necessarily relatively stiff spring means to pull the collapsed toggle joint toward its straightened position prior to the spring-biasing means reaching a dead center position. This undesirable drift of the toggle joint lessens the extent of movement of the spring-biasing means over center. This in turn diminishes the snap action force with which the spring-biasing means drives the toggle joint to the straightened position. The diminution of snap action force reduces the speed of movement of the contact arm structure toward a closed position. The improved latching mechanism or interlock means in accordance with this invention prevents this drift of the toggle joint and insures that the maximum possible closing force is available. Accordingly, an object of this invention is to provide a molded case circuit breaker of relatively large current-carrying capacity having an improved latching mechanism that restrains a contact arm structure from movement toward closed position until an overcenter spring-biasing means has moved beyond its dead center position.

Another object is to provide a molded case circuit breaker having an improved contact arm latching mechanism which, following tripping of the circuit breaker by a current-responsive tripping means, is restored to its latched condition by merely resetting the current-responsive tripping means.

Another object is to provide a molded case circuit breaker having an improved contact arm latching mechanism which eliminates the drift of a collapsible toggle joint toward a straightened position while an overcenter spring-biasing means is being moved to and through an overcenter position with respect to the toggle joint.

Another object is to provide a circuit breaker having an improved contact arm latching mechanism which maximizes the snap action force of a collapsible spring-biased toggle joint thereby to increase the impetus of movement of the contact arm structure toward a closed position and ensure the full utilization of the available spring force.

Another object is to provide a multipole molded case circuit breaker having ganged contact arm structures with an improved contact arm latching mechanism which interlocks with a single associated toggle mechanism to restrain initial movement of all of the ganged contact arm structures toward contact-closed position. I

Further objects and advantages will become apparent from the following description wherein reference is made to the drawings, in which:

FIG. 1 is a top view of a toggle mechanism, contact arm structure, and a manual operating mechanism of a molded case circuit breaker and embodying a contact arm latching mechanism in accordance with this invention, a portion of the manual operating mechanism being cut away;

FlG. 2 is a sectional view taken generally along the line 2-2 of FIG. 1 and showing the toggle mechanism in a tripped position and the contact arm structure in an open position;

FlG. 3 is a sectional view similar to FlG. 2 but showing the toggle mechanism in a set position and the manual operating mechanism during its movement in the direction of the arrow toward an ON position;

FIG. 3a is an enlarged fractional view of the contact arm latching mechanism as shown in FlG. 3;

FlG. 4 is a sectional view similar to F IG. 3 but showing the toggle mechanism in a straightened position and the contact arm structure in a contact-closed position;

FlG. 5 is a top view of a ganged contact arm structure for a multipole molded case circuit breaker showing how the invention is applied thereto; and

FlG. 6 is an end view of a contact arm latch of the latching mechanism of the invention.

For the purpose of disclosing the invention, an operating mechanism for the center pole of a three-pole circuit breaker is illustrated and only as much of the circuit breaker is included as is necessary for a full understanding. It is to be understood, however, that the invention is not limited to use in a three-pole circuit breaker, but is applicable to circuit breakers regardless of the number of poles.

A toggle mechanism 10 and a contact arm structure 11 for a three-pole molded case circuit breaker having a contact arm latching mechanism in accordance with the invention and which includes a contact arm latch 13 are shown in F168. 1- 4. The toggle mechanism 10 and the contact arm structure 11, with the exception of the contact arm latching mechanism, are similar to that disclosed in the above-mentioned US. Pat. No. 3,355,685 to which reference may be made for a more detailed description of certain features of the circuit breaker.

The toggle mechanism 10 is positioned between a frame structure comprising a pair of parallel-spaced frame members 16 which may be secured to a bottom wall of a circuit breaker housing by bolts (not shown) received in respective openings in respective flange portions 16a. The contact arm structure 11 includes a rockable elongated carrier plate 18 which carries three movable contact arms 19 including a pair of outer main contact arms 19a and a central arcing contact arm 19b, The carrier plate 18 is mounted between the frame members 16 for rocking about a horizontal pivot 20 fixedly secured at .its ends to the frame member 16, respectively. The carrier plate 18, upon rocking about its pivot 20, moves the main and arcing contact arms 19a and 19b to and from their open and closed positions with respect to stationary contacts (not shown).

The contact arm latch 13 is a generally resilient member and is mounted on the upper surface of the carrier plate 18 intermediate of its lengthby securing a base portion 13a of the latch to the carrier plate 18 as by rivets 22. An upstanding curved leg portion 13b of the latch 13 has a laterally protruding portion 13c, as best shown in FlGS. 5 and 6, defining a latching surface 13d along a bottom edge thereof.

Pivotally mounted between the frame members 16 on a pivot 23 is a rockable manual operating mechanism 25. The mechanism 25 comprises a pair of spaced side members 25a, only one of which is shown, and which are bridged by a top member 25b to which a conventional handle (not shown) may be attached. The mechanism 25 is rockable as a unit between an OFF position and an ON position of the circuit breaker corresponding respectively to the open and closed positions of the contact arm structure 11 as will become apparent. Between the side members 25a is a reset roller 27 mounted on and rotatable about a pivot 28 secured at its respective ends to the side members. The reset roller 27 serves both as a resetting means for resetting a portion of the toggle mechanism 10 and as an interlock defeating means to release the contact arm latching mechanism for the contact arm structure 11 in a manner to be described.

The toggle mechanism 10 includes a cradle 30 comprising a pair of parallel and laterally spaced cross arms or cradle members 30a and 30b mounted for rocking as a unit between a tripped position (FlG. 2) and a set position (FIGS. 3 and 4) about a fixed pivot shaft 31 connected at its ends to the respective frame members 16. Each cradle member 300 and 30b has a cam surface 32 positioned to be engaged by the reset roller 27 when the manual operating mechanism is moved in a counterclockwise direction as viewed in- FIGS. 2 through 4. When so engaged, the mechanism 25 rocks the cradle 30 about the axis of the pivot 31 in a counterclockwise direction from the position shown in FIG. 2 to the position shown in FIGS. 3 and 4. The cradle members 30a and 30b, on respective portions spaced beyond the cam surfaces 32 in a direction away from the pivot 31, are linked together by a roller 33 which is arranged to operate a cradle latching mechanism 34 to set or latch the cradle 30, as will be described.

An upper edge face of the cradle member 30a adjacent the shaft 31 is formed with a latch-receiving notch or groove 35 defining an upwardly-facing latching shoulder portion 36 for engagement with and disengagement from the latching surface 13d of the latch 13. V

Thus, the cradle 30 of the toggle mechanism 10 comprises part of the contact arm latching mechanism. The latching shoulder portion 36 rotates counterclockwise about the shaft 31 when the cradle 30 rotates counterclockwise as a result of engagement between the roller 27 of the manual operating mechanism 25 and the cam surfaces 32 of the cradle members 311a and 30b as the mechanism 25 is turned counterclockwise.

Whenever this movement occurs with the carrier plate 18 in the contact open position, the latching shoulder portion 36 rotates until it engages the latching surface 13d of the contact arm latch 13 as shown in FIGS. 3 and 3a, the mechanism 25 having been returned to the position of FIG. 2.

Pivotally mounted respectively on the cradle members 30a and 30b for rocking about respective coaxial toggle pins 37 is a pair of parallel aligned links 39. The links 39 constitute part of a pair of collapsible toggle joints 40 depending respectively from the cradle members 30a and 30b. Each link 39 is pivoted at its lower end portion to an upper end portion of a companion link 41 by means of a common pivot pin 43, the links 41 comprise the remainder of the respective toggle joints 40 and the common pivot pin 43 provides a knee for the toggle joints 40 so that they operate together as a single unit between a collapsed position and a straightened position. The lower end portion of each link 41 is pivotally connected by a drive pin 45 to depending side portions of thecarrier plate 18 (see FlGS. 2-5).

An overcenter spring-biasing means 46 includes a pair of chargeable main springs 47 connected at their upper ends by a pin 49 to the top member 25b of the manual operating mechanism 25 and at their lower ends to the pivot pin 43. The main springs 47 continually urge the pin 43 upwardly and thereby, through the medium of the links 39, bias the cradle 30 to rotate in a clockwise direction as viewed in FIGS. 2 through 4. I

The cradle latching mechanism 34 comprises a pair of laterally spaced latch members 34a which are rockably mounted on a fixed pivot 51 connected at its opposite ends to the frame members 16 and accommodated in aligned slots 53 in the latch members 34a. The latch members 34a are biased in a clockwise direction, as viewed in F168. 2 through 4, by a pair of springs 55, respectively. Each spring 55 is positioned laterally between its associated latch member 34a and the adjacent frame member 16 and is connected at its lower end to a rod 56 secured at its opposite ends to latch members 34a. The springs 55 are connected at their upper ends to respective pins 58 which protrude from the inner side of the frame members 16, respectively. The springs 55 bias the latch members 34a clockwise and yieldably hold them against a suitable stop 61, mounted between the frame members 16, which limits the rocking movement of the latch members 34a in the clockwise direction. The latch members 340 are so positioned that, upon swinging of the cradle 30 counterclockwise, the roller 33 thereof engages a cam surface 62 (FIGS. 2 and 3) on each of the latch members 34a and moves the latch members 34a in a counterclockwise direction and then passes beneath a latching then return the latch members to engagement with the stop In order to latch the latch members 34 against counterclockwise rotation, a force-transmitting roller 65 (FIG. 2) extending between the upper portions of the latch members 34a cooperates with a quick trip latch of a current-responsive tripping mechanism (not shown) of the circuit breaker which may be similar to that disclosed in the above-mentioned patent to which reference may be made for a more detailed description.

1 From the foregoing description, when the contact arm structure 11 is in its contact open position and the cradle 30 of the toggle mechanism 10 is in its tripped position, as illustrated in F IG. 2, it can be seen that upon swinging the manual operating mechanism 25 counterclockwise, the roller 27, acting on the cam surfaces 32 of the cradle members 30a, swings the cradle 30 counterclockwise into its set or latched position with respect to the cradle latching mechanism 34. During this movement, the links 39 are moved downwardly by the cradle 30 forcing the pivot pin 43 to swing counterclockwise about the axis of the drive pins 45, thus increasing the tension of the main springs 47 and assuring the fully collapsed position of the toggle joints 40.

After the toggle mechanism 10 is set, upon swinging of the manual operating mechanism 25 clockwise as indicated by the arrow in FIG. 3, the main springs 47 pass overcenter to the right side of the toggle pins 37 of the toggle joints 40 so that the main springs 47 tend to swing the pivot pin 43 clockwise about the axis of the drive pins 45, and would thus cause straightening of the toggle links 39 and 41 to thereby depress the carrier plate 18 of the contact arm structure 11 for closing the contacts, except for the engagement between the latching surface 13d-and the latching shoulder portion 36 of the cradle member 30a.

Continued movement of the manual operating mechanism 25 clockwise, while the contact arm structure 11 and toggle joints 40 are held stationary by the contact arm latching mechanism, results in the tension of the main springs 47 being greatly increased. Additional clockwise movement of the mechanism 25 causes the reset roller 27 to strike the top portion of the upstanding leg portion 13b and the laterally protruding portion 13c of the contact arm latch 13 so as to remove the latching surface 13d from engagement with the latching shoulder portion 36. The additional bias of the main springs 47 acting through the links 39 and 41, pivot pin 43, and drive pins 45 abruptly drives the contact arm structure 11 to its closed position.

By this same action, the line of force of the main springs 47 is brought to the right of the pivot 23 of the manual operating mechanism 25 and thus the main springs 47 hold the mechanism 25 in the ON position of the circuit breaker. It will be seen that when in this position, should the cradle 30 be released, the main springs 47, acting through the medium of the links 39 and pivot pin 43, swing the cradle 30 clockwise and pull upwardly on the links 41, thereby moving the contact arm structure 11 to the contact open position of FIG. 2 with a snap action.

FIG. 5 shows a multipole contact arm structure 67 comprising three single contact arm structures 11 which are fastened together by a common crossbar 68 and separated by phase barriers 69. The multipole contact arm structure 67 is used in three-pole electric circuit breakers having a toggle mechanism for the center pole and provides a center pole and two outer poles, respectively. The contact arm structure 11 of the center pole is secured to the crossbar 68 by means of a bracket71, and the contact arm structures 11 of the two outer poles are secured to the crossbar 68 by means of brackets 73, respectively, thus enabling the three contact arm structures 11 to move simultaneously as a unit. The contact arm structure 11 of the center pole has the contact arm latch 13 mounted on its upper surface by means of the rivets 22. As the shoulder 36 of the cradle 30 releases the contact arm latch 13in the manner heretofore described, the contact arm structure 11 of the center pole is driven toward its contact closed position and simultaneously drives the contact arm structures 11 of the two outer poles to their contact closed position by means of the crossbar 68. Thus, it is seen that only'a single contact arm latching mechanism, in accordance with the present invention, is needed to effect simultaneous closing of a ganged concuit breakers.

lclaim:

1. In an electric circuit breaker having a pivotable contact arm structure movable between an open position and a closed position, a toggle mechanism including a pivotable cradle movable between a set position and a tripped position, a collapsible toggle joint movable between'a collapsed position and a straightened position for actuating the-contact arm structure between the open and closed positions, respectively, when the cradle is in its set position, a manual operating mechanism movable between an OFF position and an ON position and including a means to move the cradle from its tripped position to its set position as the manual operating mechanism is moved to the OFF position, and an overcenter spring-biasing means connected between the manual operating mechanism and the toggle joint for actuating the toggle joint between the collapsed and straightened positions when-the manual operating mechanism is moved substantially to the OFF and ON positions, respectively, the improvement comprising releasable complementary interlock means on the contact arm structure and cradle, respectively, effective when the cradle is in the set position and the manual operating mechanism is in the OFF position to prevent movement of the cont'act arm structure to its closed position until the biasing 'means is substantially beyond its overcenter position andin a state of increased tension as ,a result of movement of the manual operating mechanism substantially to the ON position, and interlock defeating means on said manual operating mechanism for detact arm structure, such as the structure 67, for multipole cirwhen the contact arm structure is in said open position so that, upon movement of said manual operating mechanism toward ON position, the roller engages the contact arm latch to force the latching surface out of latching engagement with the com- I plementary latching shoulder on the cradle thereby to defeat the releasable interlock means.

4. An electric circuit breaker as claimed in claim 3 wherein the contact arm latch is generally L-shaped and has a base portion secured to said contact arm structure.

5, An electric circuit breaker as claimed in claim 4 wherein the portion of the contact arm latch extending outwardly from the contact arm structure has a laterally extending portion an edge of which defines the latching surface.

6. In a circuit breaker having an elongated contact arm structure pivotable about one end portion in one direction to.

an open position and in an opposite direction to a closed position, a tog le mechanism including a releasably latchable cradle pivota le about one end portion mone direction to a set position and in an opposite direction to a tripped position, said toggle mechanism also including a collapsible toggle joint movable to a collapsed position and to a straightened position for driving the contact arm structure to the open and closed positions, respectively, a manual operating mechanism pivotable in one direction to an OFF position and in an opposite direction to an ON position, means for pivoting the cradle from its tripped position to its set position when the manual operating mechanism is moved substantially to the OFF position, and an overcenter spring biasing means connected between the manual operating mechanism and the toggle joint for driving the toggle joint to the collapsed position when the spring biasing means is moved to a first overcenter position with respect to the toggle joint in response to the movement of the manual operating mechanism substantially to the OFF position and for driving the toggle joint to the straightened position when the spring biasing means is moved to a second overcenter position with respect to the toggle joint in response feating the interlock means upon further movement of the 1 manual operating mechanism [toward the ON position, whereby the toggle joint straightens under the force of the increased tension of the biasing means to drive the contact arm structure to its closed position, the interlock means comprising a contact arm latch fixedly secured'to the contact arm structure and a complementary latching shoulder on the cradle and positioned adjacent the contactfarm latch when the contact arm structure is in its open position, and the contact arm latch including a latching surface latched with the latching shoulder on the cradle when the cradle is in its set position and the contact arm structure is in its open position.

2. A circuit breaker as claimed in claim 1 wherein the contact arm latch comprises a resilient member extending outwardly from the contact armstructure and including said latching surface.

3. An electric circuit breaker as claimed in claim 2 wherein the interlock defeating means on v the manual operating mechanism includes a roller which travels in an arcuate path detennined by pivotable movement of the manual operating mechanism, the contact arm latch lies in the arcuate path to the movement of the manual operating mechanism substantially to the ON position, the improvement comprising a contact arm latch fixedly secured to the contact arm structure generally intermediately thereof, said contact arm latch hav- I ing a latching surface spaced above and facing toward the contact arm structure, a latching shoulder on an end portion of the cradle positioned adjacent the contact arm latch when the contact arm structure is in its open position, said latching shoulder portion facing away from the contact arm structure and engaging the latching surface on the contact arm latch when the cradle is in the set position and the contact arm structure is in its open position, thereby preventing movement of the contact arm structure to its closed position until the spring-biasing means is substantially beyond its second overcenter position and in a state of increased tension as a result of movement of the manual operating mechanism substantially to the ON position, and means on the manual operating mechanism for mechanically driving the contact ann latch out of engagement with the cradle thereby to efiect movement of the contact arm structure to the closed position. 

1. In an electric circuit breaker having a pivotable contact arm structure movable between an open position and a closed position, a toggle mechanism including a pivotable cradle movable between a set position and a tripped position, a collapsible toggle joint movable between a collapsed position and a straightened position for actuating the contact arm structure between the open and closed positions, respectively, when the cradle is in its set position, a manual operating mechanism movable between an OFF position and an ON position and including a means to move the cradle from its tripped position to its set position as the manual operating mechanism is moved to the OFF position, and an overcenter spring-biasing means connected between the manual operating mechanism and the toggle joint for actuating the toggle joint between the collapsed and straightened positions when the manual operating mechanism is moved substantially to the OFF and ON positions, respectively, the improvement comprising releasable complementary interlock means on the contact arm structure and cradle, respectively, effective when the cradle is in the set position and the manual operating mechanism is in the OFF position to prevent movement of the contact arm structure to its closed position until the biasing means is substantially beyond its overcenter position and in a state of increased tension as a resulT of movement of the manual operating mechanism substantially to the ON position, and interlock defeating means on said manual operating mechanism for defeating the interlock means upon further movement of the manual operating mechanism toward the ON position, whereby the toggle joint straightens under the force of the increased tension of the biasing means to drive the contact arm structure to its closed position, the interlock means comprising a contact arm latch fixedly secured to the contact arm structure and a complementary latching shoulder on the cradle and positioned adjacent the contact arm latch when the contact arm structure is in its open position, and the contact arm latch including a latching surface latched with the latching shoulder on the cradle when the cradle is in its set position and the contact arm structure is in its open position.
 2. A circuit breaker as claimed in claim 1 wherein the contact arm latch comprises a resilient member extending outwardly from the contact arm structure and including said latching surface.
 3. An electric circuit breaker as claimed in claim 2 wherein the interlock defeating means on the manual operating mechanism includes a roller which travels in an arcuate path determined by pivotable movement of the manual operating mechanism, the contact arm latch lies in the arcuate path when the contact arm structure is in said open position so that, upon movement of said manual operating mechanism toward ON position, the roller engages the contact arm latch to force the latching surface out of latching engagement with the complementary latching shoulder on the cradle thereby to defeat the releasable interlock means.
 4. An electric circuit breaker as claimed in claim 3 wherein the contact arm latch is generally L-shaped and has a base portion secured to said contact arm structure.
 5. An electric circuit breaker as claimed in claim 4 wherein the portion of the contact arm latch extending outwardly from the contact arm structure has a laterally extending portion an edge of which defines the latching surface.
 6. In a circuit breaker having an elongated contact arm structure pivotable about one end portion in one direction to an open position and in an opposite direction to a closed position, a toggle mechanism including a releasably latchable cradle pivotable about one end portion in one direction to a set position and in an opposite direction to a tripped position, said toggle mechanism also including a collapsible toggle joint movable to a collapsed position and to a straightened position for driving the contact arm structure to the open and closed positions, respectively, a manual operating mechanism pivotable in one direction to an OFF position and in an opposite direction to an ON position, means for pivoting the cradle from its tripped position to its set position when the manual operating mechanism is moved substantially to the OFF position, and an overcenter spring biasing means connected between the manual operating mechanism and the toggle joint for driving the toggle joint to the collapsed position when the spring biasing means is moved to a first overcenter position with respect to the toggle joint in response to the movement of the manual operating mechanism substantially to the OFF position and for driving the toggle joint to the straightened position when the spring biasing means is moved to a second overcenter position with respect to the toggle joint in response to the movement of the manual operating mechanism substantially to the ON position, the improvement comprising a contact arm latch fixedly secured to the contact arm structure generally intermediately thereof, said contact arm latch having a latching surface spaced above and facing toward the contact arm structure, a latching shoulder on an end portion of the cradle positioned adjacent the contact arm latch when the contact arm structure is in its open position, said latching shoulder portion facing away from the contact aRm structure and engaging the latching surface on the contact arm latch when the cradle is in the set position and the contact arm structure is in its open position, thereby preventing movement of the contact arm structure to its closed position until the spring-biasing means is substantially beyond its second overcenter position and in a state of increased tension as a result of movement of the manual operating mechanism substantially to the ON position, and means on the manual operating mechanism for mechanically driving the contact arm latch out of engagement with the cradle thereby to effect movement of the contact arm structure to the closed position. 